The foundation of the ocean food chain is eroding, and global warming is partly to blame.

This undated handout image provided by Karl Brunn, Nostoca Algae Laboratory, shows a number of marine diatom cells (Rhizosolenia setigera), which are an important group of phytoplankton in the oceans. — Photo courtesy of Nikon Small World

Importance of phytoplankton

The food web

Phytoplankton are the foundation of the aquatic food web, the primary producers, feeding everything from microscopic, animal-like zooplankton to multi-ton whales. Small fish and invertebrates also graze on the plant-like organisms, and then those smaller animals are eaten by bigger ones.

Phytoplankton can also be the harbingers of death or disease. Certain species of phytoplankton produce powerful biotoxins, making them responsible for so-called “red tides,” or harmful algal blooms. These toxic blooms can kill marine life and people who eat contaminated seafood.

Phytoplankton cause mass mortality in other ways. In the aftermath of a massive bloom, dead phytoplankton sink to the ocean or lake floor. The bacteria that decompose the phytoplankton deplete the oxygen in the water, suffocating animal life; the result is a dead zone.

This undated handout image provided by Karl Brunn, Nostoca Algae Laboratory, shows a number of marine diatom cells (Rhizosolenia setigera), which are an important group of phytoplankton in the oceans. — Photo courtesy of Nikon Small World